Asymmetric [2 + 2] cycloaddition reaction catalyzed by a chiral titanium reagent
摘要:
In the presence of certain Lewis acids, alkenes containing an alkylthio group (for example, ketene dithioacetals, alkenyl sulfides, alkynyl sulfides, and allenyl sulfides) react with electron deficient olefins to give the corresponding cyclobutane, cyclobutene, or methylene cyclobutane derivatives. By employing a chiral titanium catalyst generated in situ from dichlorodiisopropoxytitanium and a tartrate-derived chiral diol, the [2 + 2] cycloaddition reaction proceeds with high enantioselectivity.
[2+2] Cycloaddition Reaction between Allenyl Sulfides and Electron Deficient Olefins Promoted by Lewis Acids
作者:Yujiro Hayashi、Shigeo Niihata、Koichi Narasaka
DOI:10.1246/cl.1990.2091
日期:1990.11
Methylenecyclobutane derivatives are prepared by the Lewis acid promoted [2+2] cycloaddition reactions of 1-substituted-1-methylthio-1,2-propadienes and electron deficient olefms. The asymmetric [2+2] cycloaddition of the allenyl sulfides also proceeds in high enantioselectivity by the use of a chiral titanium reagent.
BF3ÅEOEt2 Catalyzed [4+2] Cycloaddition Reactions of N-Aryl Schiff's Bases with 1-Alkenyl, 1,2-Propadienyl, and 1-Alkynyl Sulfides
作者:Koichi Narasaka、Takanori Shibata
DOI:10.3987/com-92-s(t)98
日期:——
[4+2] Cycloaddition reaction proceeds between N-aryl Schiff's bases and I-alkenyl sulfides, a 1,2-propadienyl sulfide, or 1-alkynyl sulfides in the presence of BF3.OEt2 to provide 2-substituted quinoline derivatives. A 2-alkyl-4-quinolone alkaloid, leptomerine, is prepared by applying the present cycloaddition reaction.
HAYASHI, YUJIRO;NIIHATA, SHIGEO;NARASAKA, KOICHI, CHEM. LETT.,(1990) N1, C. 2091-2094